- Email: [email protected]
Potential role of chemokines in human renal disease
f Nephrol Spotlighting new and provocative developments in world nephrology and featuring nephrologists who occupy leadership roles
Manuel Martinez-Maldonado,
MD
Editor-at-Large
Potential
Role of Chemokines Renal Disease
in Human
Rolf A.K. Stahl, MD
I
NFILTRATING leukocytes are a hallmark of almost any renal disease and mediate the initiation and progression of damage either by direct cytotoxicity, the secretion of soluble factors, or the regulation of the immune response. Before leukocytes can be mediators of disease, however, they have to reach the site of injury by moving out of the blood vessels into the interstitium. A general concept suggests that tissue damage (by infectious, immunologic, metabolic, or toxic lesions) leads to the release of soluble proinflammatory cytokines. The release of cytokines activates anchoring molecules on leukocytes (integrins) that go from a low-affinity to a high-affinity state and initiate a strong binding to endothelial counterreceptor molecules (ICAM- I, EL/&I-l). This interaction stops the leukocytes that are rolling along the endothelium (a phenomenon that is regulated by another group of molecules, the selectins) and brings the leukocytes to a firm adhesion. Leukocytes then undergo cytoskeletal changes and migrate across the endothelium into the tissue. Depending on the nature of the initial lesion, they kill pathogens and destroy or repair tissue. Leukocyte migration out of the blood vessel into the tissue is mediated by chemoattractants. Among the various chemoattractants, chemokines, a. family of small cytokines, are particularly important. Chemokines are cationic glycoproteins with molecular weights ranging from 7 to 1.5kd and strong binding affinity to proteoglycans. Almost 30 human chemokines are known. The chemokines are divided into two groups and classified according to their amino acid sequence. Most chemokines contain four cystein residues in their molecular structure and, according to whether the first two amino acids from the N-ter-
American
Journal
of Kidney
Diseases,
Vol 30, No 3 (September),
minus are directly adjacent, they are named -C-C- or ,&chemokines or -C-X-C- or or-chemokines when another amino acid residue separates the two cysteins. The structural distinctions of the chemokines are important since they are associated with some preferential effects on leukocyte subsets. Thus, the crchemokines particularly act on neutrophils and the ,& chemokines act on monocytes, lymphocytes, and eosinophils. The prototype of the cr-chemokines is interleukin-8 (IL-Q. The most intensively studied chemokine of the -C-C- subfamily is monocyte chemoattractant protein- 1 (MCP- 1). Chemokines are produced in a wide variety of cell types, including inflammatory cells, fibroblasts, endothelial, and epithelial cells. In the kidney, tubular, mesangial, vascular, and glomerular endothelial cells secrete chemokines. Chemokines are expressed rapidly following the activation of cells by proinflammatory cytokines, such as tumor necrosis factor(Y, IL-1,0, or lipopolysaccharides, and immune complexes. Steroids, IL-4, IL-IO, transforming growth factor-p, and prostaglandins are endogenous repressors of chemokine secretion. Chemokines induce their actions by binding to cell-specific receptors that belong to the family of Gprotein-linked seven transmembrane-spanning molecules. Ligand-receptor interaction is specific for one chemokine (ie, IL-S) or more than one chemokine binds to an individual receptor. Ligand binding to the receptors leads to activation of phospholipases, inosit01 triphosphate, and diacyglycerol with an increase of intracellular calcium and activation of protein kinases. Chemokines induce different actions, including migration of leukocytes, release of oxygen radicals, activation of integrins, and others, which may be mediated by several other kinases.
1997:
pp xlix-Iii
xlix
OF NEPHROLOGY
I
Both substances are involved in leukocyte recruitment in renal injury. IL-8 and MCP-1 have been studied. Intensive work in cultured cells in vitro revealed that growth factors (platelet-derived growth factor), inflammatory cytokines (IL-ID, tumor necrosis factor-a, y-interferon), peptide hormones (angiotensin II), lipopolysaccharides, and immune complexes induce the expression and secretion of IL-8 and MCP-1. The first in vivo evidence that chemokines may be involved in renal disease is derived from a rat model of acute renal failure, where increased tubular MCP-1 expression was found. Since neutrophils and monocytes particularly play a predominant role in diverse forms of glomerulonephritis, most studies focus on these lesions. In the rat model of anti-thy-l glomerulonephritis,
AND
NEPHROLOGISTS
glomerular immune complex formation induces a marked increase of the mRNA expression and protein secretion of MCP-1. This induction appears within 30 minutes to 1 hour, is complement dependent, remains elevated for a few clays, and then normalizes. The expression of MCP-1 is paralleled by the glomerular influx of monocytes, which reach a maximum at 24 hours and then decrease over the following days. This pattern of increased MCP-1 expression and appearance of monocytes has been reported in several animal models of immune and nonimmune renal injuries. Treatment of glomerulonephritis with neutralizing antibodies against MCP-1 results in an almost complete blockade of the chemotactic activity in glomeruli and the reduction of infiltrating monocytes by 40%. In addition, anti-MCP- 1 antibody treatment ameliorates the for-
‘of the mesang&m, tid answ&s to‘questions-about its role in glomerular diicascs w&e beginriing to be _~ . Professor of Medicine extracled in increasin’gquarititics and to’ filter into ihe’ Head, Division of Nephrology and Osteol&!jy I literature. Stahl contributed with. significant stud& UKE-Medizinische Klinik on the role of pi-osranoidsin the glomerular injury of Universitats-Krankenhaus Eppendorf experimental glomerulonephritis. Yet, in addition to Hamburg, Germany ,,‘1 .,, the important work on the pathophysiology of inesanln: gial injury, Stahl continued to be intTiiucd by the contribution of these cells to the physiology of glomeruThe busy industrial city of lar l’unction. In such a- complex structure as theI Iamburg, where Professor Rolf A.K. Stahl now teaches, glomerulus, it is inevitable to have a multiplicity of may have its charms, but the factors influence its structure and function. Questions’ city exists in stark contrast to soon arose on the relationship between a seriesof horthe beauty of the Black Forest mones such as angiotensin II, prostaglandins, 6nd atriregion in the federal state of al natriuretic factor, and the expression and regulatiod Radcn-Wiirttcmberg. Thcrc, in of gents coding proteins involved in gldmcrular the town of Miihlacker, Rolf metabolism. Thus, the role of the collagen synthesis A.K. Stahl was born in the late promoter and metalloproteinase inhibitor transform^ ~_ .-. 1940s.He grew up in the area, not I&r from the waters, mg growth factor-* has been a stgnificant intcrcst 01 at Baden-Radcn, and attended medical school at both Stahl’s, Also; and increasingly, Stahl and’his coworkHohenheim and Tiibingen, receiving his MD degree _ crs have turned their attention to chcmoattractant molfrom the latter in 1975. ccules in an effort to further uhderstand the mccha-,: After his internship, Stahl entcrcd a residency in nisms by which disease damdges the precious Strucpathology, which undoubtedly prepared him for some: turc that is the glomcrulus. : of his rcccnt work. In an inspired move in 1978, Staht .’ As a result of his contributions, Stahl was appo&ed went to Buffalo, NY, where he enjoyed the almost dc an associat,eprofessoi of medicine at the Universitj; of’ rigcur honeymoon with physiology that characterized.: Frankfurt in 1987, and in 1993 hc was named the decade.There he worked in JamesB. Ire’s groupProfessor of Medicine and he& of tbc Division of in the division of hypertension,a group that performed Nephrology in the Department of Medicine at the some of the earliest work in the blossoming field of’ University of Hafihurg; ‘Stahl is undoubtedly one of prostaglandins,biochemistry. and physiology. the new breed of German nephrologist who, as his Back in Germany, Stahl completed his residency in 1 training attests,is neverthelesssteepedin’the traditions internal medicine in the program at the University of begun by the likcsof Virch‘owand Henle. Stahl, a softFrcihurg. After a parenthetical assignment in that spoken, incisive interlocutor, is a dedicated family institution as assistanr professor, he traveled to’ .’ man (dad to three boys) a’nda runner-of several miles Seattlc, WA, in 1985 for a fellowship in William G.: a week. Mente agilr in corpora SRIEO. Causer’s laboratory. It was the mid-time of the cpoch-Manuel Martinez-Mddtimdo, MD
Rolf A.K. Si tahl, MD,
.
_
__
-.
-
OF NEPHROLOGY
AND
NEPHROLOGISTS
mation and deposition of extracellular matrix components and the progression of disease. A role for chemokines in the recruitment of neutrophils was also demonstrated in rabbit and rat models of anti-glomerular basement membrane nephritis. Neutralizing antibodies against IL-S or the IL-S homologue cytokine-induced neutrophil chemoattractant (CINC) resulted in a 40% reduction of glomerular polymorphonuclear granulocytes (PMN) infiltration, which was associated with the improvement of renal injury. Evidence has also accumulated that chemokines are involved in human renal disease. Using immunohistology or in situ hybridization techniques, several investigators demonstrated the expression of MCP-I , Regulated upon Activation Neutral T-cell Expressed and Secreted (&ANTES; a C-C- chemokine), and IL-S in renal tissues of patients with proliferative glomerulonephritis, tubulointerstitial diseases, and renal allograft rejection. Expression of the chemokines in glomerular or tubular cells was in most cases anatomically adjacent to the infiltrating leukocytes, which would argue for a causal functional relationship. Additionally, investigators found increased urinary excretion of MCP-I and IL-8 in renal diseases characterized by high inflammatory cell infiltration, such as lupus nephritis and vasculitis. There is no information on whether specific patterns of chemokine expression, which might correlate with specific stages of renal injury and specific cell types, exist in kidney disease. In addition, there is no evidence of a functional role for chemokines in human tissue, such as has been described for the animal models. What other functions do chemokines have? Besides their chemoattractant activity, chemokines also activate leukocytes. IL-8 induces superoxide and granule release from neutrophils and plays a role in angiogenesis in endothelial cells. Similarly, MCP1 stimulates superoxide formation, releases arachidonic acid metabolites from monocytes, and induces collagen formation in fibroblasts.
Ii
An important role of chemokines and chemokine receptors in human immunodeficiency virus (HIV) infection is emerging. It has been characterized that CD8 T-cell-derived inhibitors of HIV replication are probably largely related to the ,0-chemokines RANTES, MIP-lor, and MIP-lp. This may be due to increased chemokine formation with increased binding to chemokine receptors, allowing HIV entry into monocytes/macrophages or T cells. Does the role of chemokine on leukocyte recruitment make them targets for rational therapies? The antibody studies in animal models also support such a strategy in humans. Furthermore, blocking experiments with modified chemokines, which bind to the receptor but do not induce signaling, could neutralize the effects of endogenously formed molecules. This strategy already has been demonstrated to be effective in vitro. One has to consider the potentially noxious effect that chemokines probably play in host defense, since long-term suppression of this function could be associated with a dramatic loss of protection against viral or bacterial infection. Therefore, the role of the individual chemokines in distinct renal diseases must be better characterized to develop specific therapeutic strategies. We also have to understand better whether there are specific patterns of chemokine formation in individual diseases that also might be related to certain stages of the disease. There are undoubtedly more questions than answers in this exciting field, but a better understanding of the role of chemokines in kidney disease may enhance our chances for therapeutic options,
Do you have news items? Send nephrology-related appointments. promotions, awards, research, and other news items to Manuel Martinez-Maldonado, MD, at 404-235-3001 (phone), 404-235-3005 (fax), or [email protected] (e-mail). Announcements and call for priyes and awards will not appear in this section.
J
Manuel Martinez-Maldonado,
MD
Editor-at-Large
Potential
Role of Chemokines Renal Disease
in Human
Rolf A.K. Stahl, MD
I
NFILTRATING leukocytes are a hallmark of almost any renal disease and mediate the initiation and progression of damage either by direct cytotoxicity, the secretion of soluble factors, or the regulation of the immune response. Before leukocytes can be mediators of disease, however, they have to reach the site of injury by moving out of the blood vessels into the interstitium. A general concept suggests that tissue damage (by infectious, immunologic, metabolic, or toxic lesions) leads to the release of soluble proinflammatory cytokines. The release of cytokines activates anchoring molecules on leukocytes (integrins) that go from a low-affinity to a high-affinity state and initiate a strong binding to endothelial counterreceptor molecules (ICAM- I, EL/&I-l). This interaction stops the leukocytes that are rolling along the endothelium (a phenomenon that is regulated by another group of molecules, the selectins) and brings the leukocytes to a firm adhesion. Leukocytes then undergo cytoskeletal changes and migrate across the endothelium into the tissue. Depending on the nature of the initial lesion, they kill pathogens and destroy or repair tissue. Leukocyte migration out of the blood vessel into the tissue is mediated by chemoattractants. Among the various chemoattractants, chemokines, a. family of small cytokines, are particularly important. Chemokines are cationic glycoproteins with molecular weights ranging from 7 to 1.5kd and strong binding affinity to proteoglycans. Almost 30 human chemokines are known. The chemokines are divided into two groups and classified according to their amino acid sequence. Most chemokines contain four cystein residues in their molecular structure and, according to whether the first two amino acids from the N-ter-
American
Journal
of Kidney
Diseases,
Vol 30, No 3 (September),
minus are directly adjacent, they are named -C-C- or ,&chemokines or -C-X-C- or or-chemokines when another amino acid residue separates the two cysteins. The structural distinctions of the chemokines are important since they are associated with some preferential effects on leukocyte subsets. Thus, the crchemokines particularly act on neutrophils and the ,& chemokines act on monocytes, lymphocytes, and eosinophils. The prototype of the cr-chemokines is interleukin-8 (IL-Q. The most intensively studied chemokine of the -C-C- subfamily is monocyte chemoattractant protein- 1 (MCP- 1). Chemokines are produced in a wide variety of cell types, including inflammatory cells, fibroblasts, endothelial, and epithelial cells. In the kidney, tubular, mesangial, vascular, and glomerular endothelial cells secrete chemokines. Chemokines are expressed rapidly following the activation of cells by proinflammatory cytokines, such as tumor necrosis factor(Y, IL-1,0, or lipopolysaccharides, and immune complexes. Steroids, IL-4, IL-IO, transforming growth factor-p, and prostaglandins are endogenous repressors of chemokine secretion. Chemokines induce their actions by binding to cell-specific receptors that belong to the family of Gprotein-linked seven transmembrane-spanning molecules. Ligand-receptor interaction is specific for one chemokine (ie, IL-S) or more than one chemokine binds to an individual receptor. Ligand binding to the receptors leads to activation of phospholipases, inosit01 triphosphate, and diacyglycerol with an increase of intracellular calcium and activation of protein kinases. Chemokines induce different actions, including migration of leukocytes, release of oxygen radicals, activation of integrins, and others, which may be mediated by several other kinases.
1997:
pp xlix-Iii
xlix
OF NEPHROLOGY
I
Both substances are involved in leukocyte recruitment in renal injury. IL-8 and MCP-1 have been studied. Intensive work in cultured cells in vitro revealed that growth factors (platelet-derived growth factor), inflammatory cytokines (IL-ID, tumor necrosis factor-a, y-interferon), peptide hormones (angiotensin II), lipopolysaccharides, and immune complexes induce the expression and secretion of IL-8 and MCP-1. The first in vivo evidence that chemokines may be involved in renal disease is derived from a rat model of acute renal failure, where increased tubular MCP-1 expression was found. Since neutrophils and monocytes particularly play a predominant role in diverse forms of glomerulonephritis, most studies focus on these lesions. In the rat model of anti-thy-l glomerulonephritis,
AND
NEPHROLOGISTS
glomerular immune complex formation induces a marked increase of the mRNA expression and protein secretion of MCP-1. This induction appears within 30 minutes to 1 hour, is complement dependent, remains elevated for a few clays, and then normalizes. The expression of MCP-1 is paralleled by the glomerular influx of monocytes, which reach a maximum at 24 hours and then decrease over the following days. This pattern of increased MCP-1 expression and appearance of monocytes has been reported in several animal models of immune and nonimmune renal injuries. Treatment of glomerulonephritis with neutralizing antibodies against MCP-1 results in an almost complete blockade of the chemotactic activity in glomeruli and the reduction of infiltrating monocytes by 40%. In addition, anti-MCP- 1 antibody treatment ameliorates the for-
‘of the mesang&m, tid answ&s to‘questions-about its role in glomerular diicascs w&e beginriing to be _~ . Professor of Medicine extracled in increasin’gquarititics and to’ filter into ihe’ Head, Division of Nephrology and Osteol&!jy I literature. Stahl contributed with. significant stud& UKE-Medizinische Klinik on the role of pi-osranoidsin the glomerular injury of Universitats-Krankenhaus Eppendorf experimental glomerulonephritis. Yet, in addition to Hamburg, Germany ,,‘1 .,, the important work on the pathophysiology of inesanln: gial injury, Stahl continued to be intTiiucd by the contribution of these cells to the physiology of glomeruThe busy industrial city of lar l’unction. In such a- complex structure as theI Iamburg, where Professor Rolf A.K. Stahl now teaches, glomerulus, it is inevitable to have a multiplicity of may have its charms, but the factors influence its structure and function. Questions’ city exists in stark contrast to soon arose on the relationship between a seriesof horthe beauty of the Black Forest mones such as angiotensin II, prostaglandins, 6nd atriregion in the federal state of al natriuretic factor, and the expression and regulatiod Radcn-Wiirttcmberg. Thcrc, in of gents coding proteins involved in gldmcrular the town of Miihlacker, Rolf metabolism. Thus, the role of the collagen synthesis A.K. Stahl was born in the late promoter and metalloproteinase inhibitor transform^ ~_ .-. 1940s.He grew up in the area, not I&r from the waters, mg growth factor-* has been a stgnificant intcrcst 01 at Baden-Radcn, and attended medical school at both Stahl’s, Also; and increasingly, Stahl and’his coworkHohenheim and Tiibingen, receiving his MD degree _ crs have turned their attention to chcmoattractant molfrom the latter in 1975. ccules in an effort to further uhderstand the mccha-,: After his internship, Stahl entcrcd a residency in nisms by which disease damdges the precious Strucpathology, which undoubtedly prepared him for some: turc that is the glomcrulus. : of his rcccnt work. In an inspired move in 1978, Staht .’ As a result of his contributions, Stahl was appo&ed went to Buffalo, NY, where he enjoyed the almost dc an associat,eprofessoi of medicine at the Universitj; of’ rigcur honeymoon with physiology that characterized.: Frankfurt in 1987, and in 1993 hc was named the decade.There he worked in JamesB. Ire’s groupProfessor of Medicine and he& of tbc Division of in the division of hypertension,a group that performed Nephrology in the Department of Medicine at the some of the earliest work in the blossoming field of’ University of Hafihurg; ‘Stahl is undoubtedly one of prostaglandins,biochemistry. and physiology. the new breed of German nephrologist who, as his Back in Germany, Stahl completed his residency in 1 training attests,is neverthelesssteepedin’the traditions internal medicine in the program at the University of begun by the likcsof Virch‘owand Henle. Stahl, a softFrcihurg. After a parenthetical assignment in that spoken, incisive interlocutor, is a dedicated family institution as assistanr professor, he traveled to’ .’ man (dad to three boys) a’nda runner-of several miles Seattlc, WA, in 1985 for a fellowship in William G.: a week. Mente agilr in corpora SRIEO. Causer’s laboratory. It was the mid-time of the cpoch-Manuel Martinez-Mddtimdo, MD
Rolf A.K. Si tahl, MD,
.
_
__
-.
-
OF NEPHROLOGY
AND
NEPHROLOGISTS
mation and deposition of extracellular matrix components and the progression of disease. A role for chemokines in the recruitment of neutrophils was also demonstrated in rabbit and rat models of anti-glomerular basement membrane nephritis. Neutralizing antibodies against IL-S or the IL-S homologue cytokine-induced neutrophil chemoattractant (CINC) resulted in a 40% reduction of glomerular polymorphonuclear granulocytes (PMN) infiltration, which was associated with the improvement of renal injury. Evidence has also accumulated that chemokines are involved in human renal disease. Using immunohistology or in situ hybridization techniques, several investigators demonstrated the expression of MCP-I , Regulated upon Activation Neutral T-cell Expressed and Secreted (&ANTES; a C-C- chemokine), and IL-S in renal tissues of patients with proliferative glomerulonephritis, tubulointerstitial diseases, and renal allograft rejection. Expression of the chemokines in glomerular or tubular cells was in most cases anatomically adjacent to the infiltrating leukocytes, which would argue for a causal functional relationship. Additionally, investigators found increased urinary excretion of MCP-I and IL-8 in renal diseases characterized by high inflammatory cell infiltration, such as lupus nephritis and vasculitis. There is no information on whether specific patterns of chemokine expression, which might correlate with specific stages of renal injury and specific cell types, exist in kidney disease. In addition, there is no evidence of a functional role for chemokines in human tissue, such as has been described for the animal models. What other functions do chemokines have? Besides their chemoattractant activity, chemokines also activate leukocytes. IL-8 induces superoxide and granule release from neutrophils and plays a role in angiogenesis in endothelial cells. Similarly, MCP1 stimulates superoxide formation, releases arachidonic acid metabolites from monocytes, and induces collagen formation in fibroblasts.
Ii
An important role of chemokines and chemokine receptors in human immunodeficiency virus (HIV) infection is emerging. It has been characterized that CD8 T-cell-derived inhibitors of HIV replication are probably largely related to the ,0-chemokines RANTES, MIP-lor, and MIP-lp. This may be due to increased chemokine formation with increased binding to chemokine receptors, allowing HIV entry into monocytes/macrophages or T cells. Does the role of chemokine on leukocyte recruitment make them targets for rational therapies? The antibody studies in animal models also support such a strategy in humans. Furthermore, blocking experiments with modified chemokines, which bind to the receptor but do not induce signaling, could neutralize the effects of endogenously formed molecules. This strategy already has been demonstrated to be effective in vitro. One has to consider the potentially noxious effect that chemokines probably play in host defense, since long-term suppression of this function could be associated with a dramatic loss of protection against viral or bacterial infection. Therefore, the role of the individual chemokines in distinct renal diseases must be better characterized to develop specific therapeutic strategies. We also have to understand better whether there are specific patterns of chemokine formation in individual diseases that also might be related to certain stages of the disease. There are undoubtedly more questions than answers in this exciting field, but a better understanding of the role of chemokines in kidney disease may enhance our chances for therapeutic options,
Do you have news items? Send nephrology-related appointments. promotions, awards, research, and other news items to Manuel Martinez-Maldonado, MD, at 404-235-3001 (phone), 404-235-3005 (fax), or [email protected] (e-mail). Announcements and call for priyes and awards will not appear in this section.
J